Hydrodynamic machine



Filed Feb. 10, 1938 2 Sheets-Sheet 1 INVENTUR WALTER FERRIS T TDRNEY.

Patented Feb. 11, 194i PATENT "OFFICE r 'nrnnonrmmc mom y Walter Ferris, Milwaukee, Wis, assignor to Th6 Oilgear Company, Milwaukee, Wis., a 00m"! tion of Wisconsin Application February 10, 1938, Serial No. 189,792 14 Claims. (01. 103-161) This invention relates to hydrodynamic machines of the type in which the cylinders are arranged in a cylinder barrel and revolve about a central valve shaft or pintle upon which the cylinder barrel is journaled to rotate thereon and through which liquid flows to andirom the cylinders, and pistons are fitted in the cylinders and react against a' thrust member which rotates with the cylinder barrel and causes the pistons to reciprocate as the cylinder barrel rotates. Such a machine will function as a pump when it is driven or it will function as a motor when it is supplied, with motive liquid When the machine is in operation, liquid from the high pressure port of the pintle seeps between the cylinder barrel and the pintle and spreads over that area of the pintle which is covered by the cylinder barrel. This liquid forms a lubricating film between the cylinder barrel and the pintle and thena part of this liquid escapes into the intake port and another part thereof escapes from the ends 0! the cylinder barrel. The total volume of liquid thus escaping from the pressure port of the pintle together with such liquid as may escape past the pistons is generally designated-as the real slip of the machine. and this slip varies in accordance with variations in the clearance between the cylinder barrel and the pintle, variations in pressure, and variations in the viscosity of the liquid which is ordinarily a good grade of lubricating oil the viscosity of which'varies as the temperature or the liquid varies: The machine also has what is known as "apparent slip which is a variation in its output due to a variation in the pressure in the motive liquid andis caused by the compressibility or-the liquid and the deflection of machine parts.

The entire or total slip may be maintained substantially constant by tapering that portion of the pintle upon which the cylinder barrel is fitted, forming a cylinder upon the end of the cylinder barrel, and fitting a piston in the cylinder so that leakage liquid escaping from the end of the pintle will enter the cylinder and urge the cylinder barrel toward the large end of the pintle as disclosed in Patent No. 2,064,299.

In the machine shown in the above patent, the thrust member is connected to the drive shaft, the end cylinder rotates relative to the piston fitted therein, and the displacement oi the machine is varied by shifting the pintle transversely oi the axis of the thrust member.

The present invention has as an object to provide means for maintaining substantially constant the slip of a hydrodynamic machine which has its cylinder barrel connected to a. drive shaft to drive-the same or to be driven thereby.

Another-object is to provide a hydrodynamic machine with a slip compensating piston and cylinder between which there is no relative rovtation.

Another object is to provide a slip compenl0 sated hydrodynamic machine the cylinder barrel of which will not adhere to' the pintle when the machine is functioning as a motor and has remained stalled under a load for a considerable period of time.

Other objects and advantages will appear from the description hereinafter given of a hydrodynamic machine in which the invention is em- According to the invention in its general aspect and as ordinarily embodied in practice, the cylinder barrel is fitted upon the tapered partoi a. stationary pintie and connected to a drive shaft to rotate therewith, an end cylinder is fixed upon the cylinder barrel and extends beyond the small end of the pintle, a piston it fitted in the end cylinder to rotate therewith and is restrained from axial movement, and liquid escaping from between the cylinder barrel and the pintle enters so the end cylinder and urges the cylinder barrel toward the large end of the pintle.

The invention is exemplified by the hydrodynamic machine shown in the accompanying drawings in which the views are as follows:

Fig. 1 is a central vertical section through the machine. Fig. 2 is a transverse section taken on the irregular line 2-2 of Fig. 1.

Fig. 3 is a sectional plan view taken on the 40 line 2-4 of Fig. 2.

Fig. 4 is a detail view of Fig. 2. For the purpose of illustratiomthe invention has been shown as being embodied in a hydrodynamic machine of the rolling piston type but it is not necessarily limited to any particular type. Since the rolling piston type 01' hydrodynamic machine is fully illustrated and described in my prior Patent 2,074,068, only as much oi the machine has been illustrated as is necessary for an understanding of the presentlnvention.

The machine has its mechanism arranged within and carried by a closed casing'l which has a removable head 2 rigidly attached to its I taken on the line 4-4 front end and a hub 3 of substantial thickness functioning as a motor as will formed integral with its rear wall.

If the displacement of the machine is to be variable, a hollow slide block 4 is arranged in casing and restrained thereby from vertical or longitudinal movement, suitable slide plates 5 and 6 are arranged between it and the upper and lower walls of casing I, as shown in Fig. 2, one or more suitable connections such as 1 and/or 8 are provided for connecting it to'means for shifting it transversely of easing, i.- according' to the usual practice, and a cylindrical thrust member 9 is arranged within slide block 4 and rotatably supported therein by two roller thrust bearings l and II which are carried by slide block 4. If-the displacement of the machine is to remain constant, thrust member 9 or the equivalent thereof is fixed in or formed integral with casing I.

Thrust member 9 causes the pistons to Ieciprocate when the machine is functioning as -a pump and it enables the pistons to cause the cylinder barrel to rotate when the machine is presently appear. A valve shaft or pintle l has the rear part thereof rigidly secured in hub 3 and the front part thereof arranged within thrust member 9 and provided with an upper segmental port l6 and a lower segmental port H which communicate, respectively, with upper and lower passages l8 and Hiformed in pintle l5 longitudinally thereof. The rear ends of passages l8 and I9 extend outward through the rear part of pintle l5v for connection to an external circuit.

is tapered toward the front end thereof and suption of cylinder barrel 20 will cause the pistons at one side of the'horizontal centerline of the machine to be moved progressively inward by thrust ring 26 and expel liquid from their cylinders into one pintle port while the pistons on the other side of that centerline are permitted to move progressively outward and their cylinders to be supplied with liquid from the other pintle port.

If the machine is to function as a motor, motive liquid is supplied thereto. The motive liquid will fiow through one pintle port to the cylinders in communication therewith and force th pistons in those cylinders outward. The outward moving pistons will react upon thrust rings 26 and, due to the eccentricity of thrust member 9, will cause cylinder barrel 20 to rotate.

Rotation of cylinder barrel 2|) either by mechanical means or by liquid will cause pistons 25 to rotate in their cylinders as they reciprocate therein due to the contact face of each piston be- That part of pintle |5 within thrust member 9 ports a cylinder barrel 20 which has a bushing 2| fixed therein to form a part thereof and accurately fitted upon the tapered part of pintle J5 to rotate thereon.

Cylinder barrel 20 is provided with a plurality of radial cylinders 22 which are arranged in circumferential rows and are ordinarily also arranged in longitudinal rows. Cylinder barrel 20 is also provided with a plurality of passages 23 each of which communicates with at least one cylinder in each of a plurality of circumferential rows. cylinder port 24 which is formed inbus'hing 21 and communicates with pintle ports l6 and I1 alternately as cylinder barrel 20 rotates.

A piston 25 is fitted in each cylinder 22 and provided with an, arcuate contact face upon its outer end or head. The contact faces on all of the pistons in each circumferential row engage a substantially conical reaction surface formed upona thrust ring 26 which extends around cylinder barrel 2!] and 'is fixed within thrust member 9,

Each passage 23 communicates with 'a the reaction surface engaging each contact face upon a single spot which is ofi'set far enough from the piston axis to cause the piston to rotate in its cylinder as it reciprocates thereim.

The reaction surfaces in contact with adjacent rows of pistons are inclined in opposite directions ing ofiset from the piston axis.

Cylinder barrel 2!! is connected, by means to be presently described, to a drive shaft 30 so that I it may rotateshaft 30 or be rotated by it. Shaft 30 is rotatably supported by a thrust bearing 3|, which is arranged in end head 2, and by a thrust bearing 32 which is arranged in a recess formed indzheend of pintle I5.

If "the machine is to be employed as a pump,

it is ordinarily provided with an auxiliary pump for supplying liquid which may be used for control purposes, for supercharging the main. pump and/or for other purposes according to the usual practice.

' As shown, the machine is provided with a gear pump consisting primarily of two gears 33 and 34 the first r which is fixed upon shaft so and the other of which is rotatably supported by means-of a roller bearing 35 upon a stub-shaft 3G fixed in end head 2. Gears 33 and 34 are fitted in a suitable pump chamber 31 which is formed in end head 2 and closedby a. plate 38 attached thereto.

The present invention does not residein the construction thus far described but is directed to providing means formaintaining the slip of the machine substantially constant. To this end, a cylinder is arranged upon the end of the cylinder barrel, 8. piston is fitted in the cylinder, and liquid escaping from between the cylinder barrel and the pintle enters the end cylinder and urgesthe cylinder barrel toward the large end of the pintle with a. force which varies in accordance with variations-1n the pressure of the motive liquid.

As shown, cylinder 20 has its body or main portion extended beyondthe smailiend of pintle I! to provide an end cylinder 4|,-the end of bushing 2| being arranged substantially flush with the end of pintle l5. As best shown in Fig. 3, end cylinder 4| is provided with an inner bore 42which is an extension of the bore in which bushing 2| is fitted, an intermediate bore 43 which is larger than bore 42, and an outer bore which is still larger.

Cylinder 4| has arranged therein a member 45 which is splined upon shaft 30 and prevented from,moving outward by a shoulder 46 formed upon shaft 30. Member 45 functions both as a so that thrust member 9 is eccentric to cylinder barrel 20, the machine will function as follows:

If it is to function as a pump, cylinder barrel 20 is rotated from an outside 'source of power. Due to the eccentricity of thrust member 9, rotapiston for closing the end of cylinder 4| and as a driver for rotating cylinder barrel 20. r

The outer or piston part of member 45 is fitted in bore 44 and provided in itsperipheral surface with a piston ring 41 which prevents liquid from escaping through the outer end of cylinder 4|. The inner or driver part of member 45 is reduced to a diameter approsimately that of bore 42 and a driving ring 48 is arranged between its peripheral surface andthe wall of bore 43.

In order that rotative forces may be trans"- mitted through driving ring 48, twodiametrically Cylinder barrel 28 is urged toward the right I in respect to Fig. l by two leaf springs 55 each of which consists of a plurality of leaves. Springs 55 extend across bore 42 upon opposite sides of shaft 38 and have their end portions arranged in two slots 56 which are formed diametrically opposite each other in the side wall of bore 42 and extend beyond the side wall of bore 43 so as to form two abutments 51 upon which the ends of springs 55 act as best shown in Figs. 1 and 2.

Springs 55 are enabled to exert a force upon abutments' 51 by a reaction member 58 which is slidable upon the reduced end portion of shaft 38 and prevented by thrust bearing 32 from moving toward the left in respect to Fig. l.

Since it is ditlicult in actual practice to so machine the parts that all of the bores for the drive shaft and pintle are in absolute alinement, a roller bearing 58 is arranged between reaction member 58 and the center of each spring 55 so that any slight misalinement will not cause relative movement between reaction member 58 and the inner race of bearing 32, as such relative movement would cause the abutting surfaces to be abraded and thereby eventually destroy the accurate adjustment of the parts.

Springs 55', by acting upon abutments 51 and reacting against reaction member 58, urge cylinder'barrel 28 toward the right in respect to Fig. 1. When the machine is idle or operating under a low pressure, springs 55 hold the end .wall of bore 43 against driving ring 48 and hold ring 48 against member 45. Since shoulder 45 on shaft 38 prevents member 45 from moving toward the right in respect to Fig. 1 and since shaft 38 is restrained from" axial movement by thrust bearing 3|, member. 45 acts as, a positive, stop for limiting the movement of cylinder barrel 28 toward the right.

Since the bearing surfaces of pintle l5 and cylinder barrel 28 are tapered, the clearance therebetween is increased by moving cylinder barrel 28 toward the right and decreased by moving it toward the left.

In order to adjust the position of member 45 and thereby determine the maximum clearance between cylinder barrel 28 and pintle I5, thrust bearing 3| is positioned by means of shims 6| which may be varied as to thickness or number to so locate shaft 38 and member 45 that, when cylinder barrel 28 is at the limit of its movement toward the right, the clearance between it and pintle I5 is just sufficient to permit a relatively low pressure to cause the motive liquid even when cold to form a lubricating film between the cylinder barrel and the pintle.

As previously explained, the liquid escaping fromthe high pressure pintle port spreads over the bearing surface of the pintle and then a part of this liquid escapes into the low pressure pintle port and another part thereof escapes from the ends of the cylinder barrel.

That part the liquid escaping past the front end of the pintle enters end cylinder 4| and creates therein a pressure which acts upon the inner faces of piston member 45 and upon the rear walls of bores 42, 43 and 44. Since piston member 45 is prevented by shoulder 48 from moving outward, the pressure in end cylinder 4| tends to move cylinder barrel 28 toward the left, to

thereby decrease the clearance between it andcommunicates through a passage 54 with the inlet of a relief valve 65 which limits the pressure in end cylinder 4|.

The rate at which liquid will flow through a restricted passage varies in accordance with variations in either or both the pressure and the viscosity of the liquid. Therefore, as the pressure or the temperature of the motive liquid increases, liquid will flow between the cylinder barrel and the pintle and into end cylinder 4| at a faster rate and thereby tend to escape through passage 82 at a faster rate.

However, the escape of liquid through passage 62 is resisted by choke 63 so that an increase in the rate of flow into cylinder 4| results in an increase in the pressure therein. Consequently, continued increase in the pressure and/or temperature of the motive liquid will cause the pressure in cylinder 4| to rise until it is high enough to'overcome'the resistance of springs 55 and then the liquid in cylinder 4| will mcve cylinder barrel 10 the pressure in end cylinder 4| As shown, movement of the cylinder barrel toward the large end of the pintle is positively limited by the end of bushing 2| engaging the hub of thrust member 9 which forms a positive stop, and the pressure in cylinder 4| is limited by a relief valve 85.

If the machine is to function as a pump, it may be provided with springs 55 which will start to yield as soon as pump pressure reaches the lower limit of the range of pressures created by the pump when doing useful work, in which case the liquid in end cylinder 4| will hold the cylinder barrel against the lubricating film with a force proportional to pump pressure and thereby prevent variations in the pressure and/or the viscosity of the motive liquid from causing a substantial variation in the slip of the pump throughout the range of working pressures.

If the machine were to function as a motor and should remain stalled for a considerable period of time under a heavy load, at which time the pressure of the motive liquid would be maximum and the clearance between the cylinder barrel and the pintle would be minimum, particles of solid matter carried by the motive liquid might and often do lodge between the cylinder barrel and the pintle and cause the cylinder barrel to grip the pintle.

It is ordinarily not especially important to the lower part of the pressure range, in which case the springs have suflicient strength to move the cylinder barrel even though particles of solid matter have lodged between it and the pintle.

It is to be understood that the cylinder barrel has but a limited movement longitudinally of the pintle. For example, the cylinder barrel in the machine shown has a total movement of approximately 1%" in each direction from theposition occupied by it when the machine is operating under a normal or intermediate pressure.

The invention herein set forth issusceptible of various modifications without departing from the scope thereof as hereafter claimed.

'The invention is hereby claimed as follows:

1. In a hydrodynamic machine. the combination of a tapered valve'shaft or pintle fixed at its large end in a stationary position and provided with intakeand discharge ports and-passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a-rotatable reactance member for reciprocating said pistons, a drive shaft connectedindependently of said member to said cylinder barrel to rotate therewith, an end cylinder arranged upon the end of said cylinder barrel and-extending beyond the small end of said pintleto collect liquid leaking from between said cylinder barrel and said pintle, a'piston fitted in said end cylinder to rotate therewith and closing the end thereof, and means other'than said pintle for restraining said piston from axial movement to thereby cause the liquid entering said end .cylinder tourge said cylinder barrel toward the large end of said pintle. I

2. In a hydrodynamic machine, the combination of a tapered Yalve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, 'a cylinderbarrel fitted upon said pintle to rotate .thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, a drive shaft arranged in axial alinement with said pintle and connected to said cylinder barrel to rotate therewith, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between :said cylinder barrel and said pintle, and a piston restrained from axial movement by said shaft and fitted insaid end cylinder to rotate therewith and closing the end of said cylinder to thereby cause the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle.

' 3. In a hydrodynamic machine, the combination of a tapered'valve' shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages,

a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a rotatable reactance member for reciprocating said pistons, a drive shaft connected independently of said member to said cylinder barrel to rotate therewith, an end cylinder arranged upon the'end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a piston fitted in said end cylinder to rotate therewith and closing the end thereof, and means other than said pintle for restraining said piston from axial movement to thereby cause the liquid entering said end cylinder to urge said cylinder barrel toward the large end of said pintle, and means providing a passage for the escape of liquid at a limited rate from said end cylinder.

4. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, a drive shaft arranged in axial alinement with said pintle and connected to said cylinder barrel to rotate therewith, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a piston restrained from axial movement by said shaft and fitted in said end cylinder to rotate therewith and closing the end of said cylinder to thereby cause the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle, and means providing a passage for the escape of liquid at a limited rate from said end cylinder.

5. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a rotatable reactance member for reciprocating said piston a jdrive shaft connected independently (if said member to said cylinder barrel to rotate therewith, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquidleaking from between said cylinder barrel and said pintle, a piston fitted in said end cylinder to rotate therewith and closing the end thereof, and means other than said pintle for restraining said piston from axial movement to thereby cause the liquid entering said end cylinder to urge said cylinder barrel toward the large end of said pintle, means providing a passage for the escape of liquid at a limited rate from said end cylinder, and a relief valve for limiting the pressure in said end cylinder.

6. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as by said shaft and fitted'in said end cylinder to,

rotate therewith and closing the end of said cylinder to thereby cause the liquid entering .said cylinder to urge said cylinder barrel toward the large end of said pintle, means providing a passage for the escape of liquid at a limited rate from said end cylinder, and a relief valve for limiting the pressure in said end cylinder.

7. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and pro-: vided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a rotatable reactance member for reciprocating said pistons, a drive shaft connected independently of said member to said cylinder barrel to rotate therewith, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a piston fitted in said end cylinder to rotate therewith and closing the end thereof, and means other than said pintle for restraining said piston from axial movement to thereby cause the liquid entering said end cylinder to urge said cylinder barrel toward the large end of said pintle, and spring means arranged within said end cylinder for urging said cylinder barrel toward the small end of said pintle.

8. In a hydrodynamic machine, the combina tion .of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, a drive shaft arranged in axial alinement with said pintle and connected to said cylinder barrel to rotate therewith, an end cyli nder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle,

a piston restrained from axial movement by said shaft and fitted in said end cylinder to rotate therewith and closing the end of said cylinder to thereby cause the liquid entering said cylinder I to urge said cylinder barrel toward the large end of said pintle, and spring means arranged within said end cylinder for urging said cylinder barrel toward the small end of said pintle.

9. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in astationary position and provided with intake and discharge ports and passages, a cylinder barre1 fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a

piston fitted in saidend cylinder to close the same, means for transmitting rotative forces between said piston and said cylinder barrel, and a drive shaft arranged in axial alinementwith said pintle and connected to said piston to rotate therewith and to prevent said piston from moving axially to thereby cause the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle.

10. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates. an end cylinder arranged upon the end of saidcylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between saidcylinder barrel and said pintle, a-piston fitted in saidend cylinder to close the same, means for transmitting rotative forces between said piston and said cylinder barrel, a drive shaft arranged in axial alinement with said pintle and connected to said piston to rotate therewith and to prevent said piston from moving axially to thereby cause the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle, and means providing a passage for the escape of liquid at a limited rate from said end cylinder.

11. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, an end cylinderarranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a piston fitted in said end cylinder to close the same, means for transmitting rotative forces between said piston and said cylinder barrel, a drive shaft arranged in axial alinement with said pintle and connected to said piston to rotate therewith and to prevent said piston from moving axially to thereby cause, the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle, and'spring means arranged within said end cylinder for urging said cylinder barre1 toward thesmall end of said pintle.

12. In a hydrodynamic machine, the combination of a tapered valve shaft or pintle fixed at its large end in a stationary position and provided with intake and discharge ports and passages, a cylinder barrel fitted upon said pintle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a piston fitted in said end cylinder to close the same, means for transmitting rotative forces between said piston and said cylinder barrel, a drive shaft arranged in axial alinement with said pintle and'connected to said piston to rotate therewith and to prevent said piston from moving axially to thereby cause the liquid entering said cylinder to urge said cylinder-barrel toward the large end of said pintle, means providing a passage for the escape of liquid at a limited rate from said end cylinder, and a relief valve for lim-l tween said cylinder barrel and said pintle, a piston fitted in said end cylinder to close the same, meansfor transmitting rotative forces between said piston and said cylinder barrel, a drive shaft arranged in axial alinement with said pintle and connected to said piston to rotate therewith and to prevent said piston from moving axially to thereby cause the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle, means for permitting liquid to escape at a limitedrate from said end cylinder, positive stops for limiting the axial movement of said cylinder barrel in each direction to thereby maintain. the clearance between said cylinder barrel and said pintle between a predetermined maximum and a predetermined minimum, and leaf springs arranged in said end cylinder upon opposite sides of said shaft for urging said cylinder barrel toward the small end of said pintle and having suflicient strength to hold said cylinder barrel against one of said stops until the pressure of the motive liquid passages, a cylinder barrel fitted upon said pin-v tle to rotate thereon and provided with cylinders which communicate with said pintle ports alternately as said cylinder barrel rotates, an end cylinder arranged upon the end of said cylinder barrel and extending beyond the small end of said pintle to collect liquid leaking from between said cylinder barrel and said pintle, a piston fitted in said'end cylinder to close the same, means for transmitting rotative forces between said piston and saidcylinder barrel, a drive shaft arranged in axial alinement with said pintle and connected to said piston to rotate therewith and to prevent said piston from moving axially to thereby cause the liquid entering said cylinder to urge said cylinder barrel toward the large end of said pintle, means for permitting liquid to escape at a limited rate from said end cylinder, positive stops for limiting the axial movement of said cylinder barrel in each direction to thereby maintain the clearance between said cylinder barrel and said pintle between a predetermined maximum and a predetermined minimum, reaction means restrained from axial movementby said pintle, roller bearings engaging said reaction means, abutments fixed for movement with said cylinder barrel, and leaf springs arranged upon opposite sides of said shaft and acting upon said abutments and reacting against'said bearings to thereby urge said cyllnder barrel toward the small end of said pintle. 1 WALTER FERRIS. 

